The present invention relates to a multilayered wiring board and a method for fabricating the same, particularly relates to a multilayered wiring board provided with reinforcing means for preventing warp and a method for fabricating the same.
Currently, high function formation and small-sized formation of an electronic apparatus using a semiconductor device of a semiconductor chip or the like has been progressed, also a semiconductor device is constituted by high density formation in accordance therewith, and multipins formation and small-sized formation thereof have been achieved. As a board mountable with a semiconductor device constituted by multipins formation and small-sized formation in this way, a multilayered wiring board utilizing a build-up method is provided.
A multilayered wiring board of this kind is constructed by a constitution constituting a core layer by a reinforcing member of a glass cloth copper plated laminated plate or the like and formed with an insulating layer and a wiring layer alternately at both faces thereof. The multilayered wiring board of the constitution can be mounted with a semiconductor device constituted by high density formation since a wiring layer thereof can be formed to be miniaturized.
However, since the multilayered wiring board includes the core layer at inside thereof, it is difficult to miniaturize a penetrated through hole formed at the core layer to pose a problem that high density of a total of the multilayered wiring board cannot be achieved. Further, there is also posed a problem that by providing the core layer, the multilayered wiring board becomes necessarily thick to hamper the small-sized formation of an electronic apparatus. Therefore, in recent years, a development of a multilayered wiring board which is not provided with a core layer has been carried out in the multilayered wiring board utilizing the build-up method (refer to Patent Reference 1).
FIG. 1 shows an example of using a multilayered wiring board 10 which is not provided with a conventional core layer as a semiconductor package. The example shown in the drawing is constructed by a constitution of mounting a semiconductor element 13 at an upper portion of the multilayered wiring board 10 and arranging a solder ball 14 at a lower portion thereof. As shown by the drawing, by not forming the core layer, thin-sized formation of the multilayered wiring board 10 can be achieved.    [Patent Reference 1]
Pamphlet of International Patent Publication No. WO2003/039219
However, there poses a problem that by simply removing the core layer functioning as a reinforcing member, warp is brought about at the multilayered wiring board owing to a difference of thermal expansion of the insulating layer made of resin and the wiring layer made of metal. When the warp is brought about, a semiconductor device or the like cannot properly be mounted to the multilayered wiring board in a mounting step to deteriorate mounting reliability. Further, there is a concern that interlayer connection of the wiring layer cannot firmly be carried out at inside of the multilayered wiring board and also reliability of the multilayered wiring board is deteriorated.
Therefore, as shown in FIG. 1, there is proposed also a constitution of arranging a reinforcing plate 11 formed with an opening portion 12 at an area of mounting the semiconductor element 13 of the multilayered wiring board 10 and reinforcing the multilayered wiring board 10 by the reinforcing plate 11. However, according to the multilayered wiring board 10 of the constitution, not only a number of parts is increased but also the multilayered wiring board 10 becomes thick by an amount of a thickness of the reinforcing plate 11.
The invention has been carried out in view of the above-described point and it is an object thereof to provide a multilayered wiring board capable of restraining warp from being brought about while achieving thin-sized formation.
In order to resolve the above-described problem, according to the invention, there is provided a multilayered wiring board including: wiring layers; and insulating layers, wherein the wiring layers and the insulating layers are laminated to form plurality of layers, and some of the plurality of laminated insulating layers are insulating layers including reinforcing members.
According to the invention, warp can be restrained from being brought about at the multilayered wiring board since the multilayered wiring board is interposed with the insulating layer including reinforcing member increasing a strength thereof by the reinforcing member.
Further, the insulating layer with the reinforcing member is constructed by a constitution of mixing the reinforcing member to a material the same as a material of other insulating layer and therefore, the insulating layer including reinforcing member can be formed and worked equivalently to other insulating layer. Therefore, warp can be restrained from being brought about while achieving thin-sized formation of the multilayered wiring board by making portions of the insulating layers constituting the multilayered wiring board function as the reinforcing members without separately providing the reinforcing members.
Further, in the invention, the insulating layer including reinforcing member may be a woven cloth or a nonwoven cloth impregnated by a resin.
Further, in the invention, the insulating layer may be formed by a resin.
Further, in the invention, the insulating layer including reinforcing members may be the resin mixed with reinforcing member.
Further, in the invention, if the plurality of laminated insulating layers are the laminated insulating layers including reinforcing members, an effect of restraining occurrence of warp is further increased.
Further, in order to resolve the above-described problem, according to the invention, there is provided a method of fabricating a multilayered wiring board including the steps of: repeatedly forming a wiring and an insulating layer by using a resin on a support board, and removing the support board, wherein in the steps of forming the insulating layers, at steps of forming portions of the insulating layers, the insulating layers are formed by a resin including a reinforcing member.
According to the invention, at the step of forming portions of the insulating layers, by simply changing the material of the insulating layer to the resin including the reinforcing member, the insulating layer functioning as the reinforcing member can be formed at a laminating center. In this way, only the material (resin) may be changed without changing the laminating step and therefore, even when the resin layer including the reinforcing member is formed at the laminating center, fabricating steps are not complicated.
Further, in the invention, the insulating layer may be made by build-up resin.
Further, if the invention further includes the steps of: pasting together two sheets of the support boards; and separating the two sheets of the support boards respectively formed with the insulating layers and the wirings, an efficiency of fabricating the multilayered wiring board is improved.
Further, if the invention further includes the steps of: respectively pasting two sheets of the support boards to a first face and a second face of a holding board holding the two sheets of the support boards; and separating the two sheets of the support boards respectively formed with the insulating layers and the wirings from the holding board, the efficiency of fabricating the multilayered wiring board is improved.
Further, the invention may further include the step of: mounting a semiconductor chip to the multilayered wiring board.
Further, in the invention, the step of removing the support board may be carried out after the step of mounting the semiconductor chip.
According to the invention, warp can be restrained from being brought about while achieving a thin-sized formation of the multilayered wiring board.